1. Field of the Invention
The present invention relates to an OSI tunnel routing method and the apparatus. More particularly, the present invention relates to an OSI tunnel routing method and the apparatus in a transmission system for a carrier.
2. Description of the Related Art
In a SONET (Synchronous optical Network) communication network, a transmission apparatus performs ADD/DROP (multiplex/demultiplex) of communication data, network state monitoring, communication path recovery when a failure occurs in the network, and the like. The transmission apparatus is managed by a monitoring apparatus called as an NMS (network management system), in which DCC byte which is provided in a header of SONET is used for management of communication between the NMS and the transmission apparatus and between transmission apparatuses. Generally, OSI (Open Systems Interconnect) is used for the protocol. OSI is formed by a stack of protocols including TL1, X.226, X.225, TP4, CLNP/IS-IS, LAPD, DCC as shown in FIG. 1. In this specification, a transmission apparatus which is connected to an OSI network is called an NE (Network Element) or a GNE (Gateway Network Element).
In the following, an OSI tunnel function will be described with reference to FIG. 2 and FIG. 3 taking an FTP service as an example. In FIG. 2, an IP (Internet Protocol) network in an NMS 10 side is IP-1, and an IP network in a GNE 12 side is IP-2. The IP-1 and the IP-2 are not directly connected by the IP protocol. When the NMS 10 in the IP-1 uses a service of an FTP (File Transfer Protocol) server 14 in the IP-2, an FTP connection request from the NMS 10 needs to be reached to the FTP server 14. However, since a Mediated-GNE 11 and a GNE 12 are connected by an OSI DCN (Data Communication Network) which does not support the TCP/IP protocol, the request can not be reached to the FTP server 14.
However, if the Mediated-GNE 11 can transfer an IP packet including the FTP connection request to the GNE 12 in the IP-2 side by using OSI, this problem can be solved. That is, when the Mediated-GNE 11 receives an IP packet destined to an IP address of the FTP sever 14, the IP packet is encapsulated by an OSI packet so that the IP packet is transferred to the GNE 12 of the IP-2 side by using OSI. Then, the IP packet is extracted from the OSI packet in the GNE 12 in the IP-2 side so that the IP packet is sent over the IP network of the IP-2. The FTP server 14 can send a response to this request to the NMS 10 in the same way. The OSI packet is a packet in which NSEL value=0x89 (0x indicates hexadecimal notation) is added to CLNP (Connection Less Network Protocol) of ISO8473 standard. FIG. 4 shows protocol stacks in a route on which data passes through the OSI tunnel.
In the conventional transmission apparatus, the OSI tunnel is statically established by a TL1 command. More particularly, as shown in FIG. 3, an IP address of the FTP server in the IP-2 and an NSAP (Network Service Access Point) address which is an OSI network address of the GNE 12 are specified as parameters for OSI tunnel setting for the Mediated-GNE 11 side. As for the GNE 12 in the IP-2, the IP address of the NMS 10 in the IP-1 and an NSAP address of the Mediated-GNE 11 should be specified. Thus, the OSI tunnel should be set by using the TL1 command in the GNEs of both IP networks.
Thus, as for the OSI tunnel function of the conventional transmission apparatus, an administrator sets or deletes the OSI tunnel function statically. Therefore, management of the transmission apparatus becomes complicated, and there is a possibility of a setting error due to manual setting. In addition, when OSI tunnels which are not used for a long time remain, there is a problem in that traffic can not be used efficiently due to occupation of bandwidth by the remained OSI tunnel.